Synthetic zeolites, which are in a narrow sense crystalline aluminosilicate, include isomorphous derivatives in which a metal atom within the framework is substituted with another metal atom. Examples of isomorphous derivatives of crystalline aluminosilicate include zincosilicate in which an aluminum atom of aluminosilicate is substituted with a zinc atom. A synthetic zeolite has uniform pores with angstrom sizes attributed to a crystal structure thereof. Taking advantage of such a feature, the synthetic zeolite has been industrially used as a molecular sieving adsorbent that adsorbs only a molecule having a particular size, an adsorption separating agent that adsorbs a molecule having strong affinity, or a catalytic base.
In the technical field of zeolites, VET refers to a particular framework structure type having a one-dimensional channel architecture. Zeolites having this structure include zincosilicate such as VPI-8 and SSZ-41 and zincoaluminosilicate. VET-type zeolites are zeolites having 12-membered rings and large pores. VET-type zeolites are promising as a catalyst for use in various hydrocarbon conversion reactions, for example as a catalyst for use in catalytic cracking, hydrocracking, dewaxing, alkylation, transalkylation, production of olefins and aromatic compounds, and the like. Conventionally, VET-type zeolites are produced exclusively by methods where a quaternary ammonium compound or the like is used as an organic structure-directing agent (hereinafter, abbreviated to “OSDA”) (see Patent Documents 1 and 2 and Non-patent Documents 1-4). Therefore, it has been believed that it is essential to use an OSDA in order to obtain the VET-type zeolite. In addition, it has been believed that it is inevitable for the synthesized VET-type zeolite to be fired so as to remove an OSDA before use because it contains the OSDA.
A synthetic method of the VET-type zeolite is, for example, as described in Patent Documents 1 and 2, and Non-patent Documents 1-4. A common method is one using a quaternary ammonium compound such as a tetraethylammonium compound as an OSDA in the coexistence of sodium ions and lithium ions. However, since said OSDA is expensive, it is not advantageous to be used industrially. In addition, since the OSDA is incorporated in the crystals of the produced zeolite, it is necessary to fire the zeolite to remove the OSDA when the zeolite is used as an adsorbent or a catalyst. Exhaust gases produced at that time are responsible for environmental pollution, and further, many drugs are required for detoxification treatment of synthesized mother liquor containing decomposition products of the OSDA. In this way, the method for synthesizing the VET-type zeolite using the OSDA is not only an expensive method but also a production method having a great environmental load. Thus, there is a need to realize a production method using no OSDAs and a VET-type zeolite essentially containing no organic matters obtained by the method.    Patent Document 1: U.S. Pat. No. 5,656,149, Specification    Patent Document 1: U.S. Pat. No. 5,591,421, Specification    Non-Patent Document 1: Journal of American Chemical Society, 1996, 118, 7299˜7310    Non-Patent Document 2: Microporous Materials, 1997, 11, 127˜136    Non-Patent Document 3: Microporous Materials, 1997, 11, 137˜148    Non-Patent Document 4: Chemistry: a European Journal, 2002, 8, 22, 5153˜5160